The invention belongs to the technical field of neurosurgery, and particularly relates to a safe cranial drill. A main drill bit is provided with main drill bit teeth, the points of the main drill bit teeth intersect at a point on the axial line, the tail end of the main drill bit is provided with raised teeth, the front end of a limit drill bit is provided with auxiliary drill bit teeth, the length of the auxiliary drill bit tooth is less than the length of the main drill bit tooth, the rear of the limit drill bit is provided with first sunken teeth, the front end of a connecting sleeve is provided with second sunken teeth, the first sunken teeth and the second sunken teeth are respectively matched with the raised teeth, a drill bit-connecting rod runs through the connecting sleeve to connect with the limit drill bit through screw threads, a conical compressed spring sleeves a centre, both the conical compressed spring and the centre are located in the drill bit-connecting rod, and a drill bit tail handle is connected with the drill bit-connecting rod through screw threads. The safe cranial drill has the following advantages: the start and stop of the safe cranial drill can be automatically controlled in the process of a surgery, the safe cranial drill can be effectively prevented from drilling through the meninges in the process of the surgery, so that the brain tissue cannot be injured, and thereby the lives of patients are ensured.